Breitling Bentley GMT Chronograph

An interesting fact that I've come to learn is that many people (even quite a few watch loving people) have no idea what a watch winder is. It is one of those things that you can show people, in action, and they still don't know what it is. I've actually had people come to my office and see a bunch of watches in winders on shelves and remark "oh really? You have to show them off like that?" Which I later learned (after some probing) was a misunderstanding thinking that a watch on a winder was so........

I hope you guys can help me out here. I recently received a very old Seamaster from my mother who purchased it for my grandfather brand-new in the late 1940s. I have done a lot of looking around and have not found any information or pictures that match this particular watch. It has a cracked crystal and is definitely not in great shape and has not been touched in any way that I can tell. I did take it to a jeweler and he said that it appeared to be authentic. Unfortunately I don't know how ........